Charging system for an energy storage in a vehicle and a method for controlling the charging system

1. A charging system for an energy storage in a vehicle comprising:

a plurality of parallelly arranged charging switch units, each charging switch unit having an input terminal configured to be connected to a common charging port, and an output terminal configured to be connected to the energy storage, wherein each charging switch unit comprises a contactor configured to control a flow of current from the charging port to the energy storage, the contactor being configured to have a controllable contact force and wherein the resistance of the contactor depends on the contact force;

for each charging switch unit, a measurement device configured to determine a parameter indicative of a resistance in a current path through the charging switch unit; and

a charging control unit connected to each of the charging switch units and configured to, if a difference in resistance between any two of the plurality of current paths is higher than a predetermined difference threshold value, control the contact force of a contactor in a charging switch unit in a current path having a deviating resistance to balance the resistances of the current paths.

2. The charging system according to claim 1 , wherein the contactor is an electromagnetic relay comprising a coil, the electromagnetic relay being configured to have a contact force proportional to a current through the coil.

3. The charging system according to claim 1 , wherein the contactor comprises a stepper motor, and wherein the contact force is controllable by controlling a position of the stepper motor.

4. The charging system according to claim 1 , wherein the measurement device configured to determine a parameter indicative of a resistance is a current meter or a voltage meter.

5. The charging system according to claim 1 , wherein the measurement device configured to determine a parameter indicative of a resistance is a temperature sensor configured to determine a temperature of the charging switch unit.

6. The charging system according to claim 5 , wherein the charging control unit is further configured to control the contact force of a contactor to reduce the current through any charging switch unit having a temperature above a predetermined threshold temperature.

7. The charging system according to claim 1 , wherein the charging control unit is further configured to control the contact force of a contactor of a charging switch unit only if a current through the charging switch unit is above a predetermined current threshold value.

8. The charging system according to claim 1 , wherein the charging control unit is further configured to determine a resistance for each current path through a charging switch unit, and if a resistance in any one current path is deviating from resistances in other current paths by more than a predetermined resistance threshold value, to control the contact force of a contactor in the one or more current path with the deviating resistance to equalize the resistance for all current paths.

9. The charging system according to claim 8 , wherein the charging control unit is further configured to select a resistance of one current path as a reference resistance and to compare resistances in the other current paths with the reference resistance.

10. A vehicle comprising a charging system according to claim 1 .

11. A method for controlling a charging system in a vehicle, the charging system comprising a plurality of parallelly arranged charging switch units, each charging switch unit having an input terminal configured to be connected to a common charging port, and an output terminal configured to be connected to an energy storage, wherein each charging switch unit comprises a contactor configured to control a flow of current in a current path from the charging port to the energy storage, the contactor being configured to have a controllable contact force and wherein the resistance of the contactor depends on the contact force, wherein the method comprises:

determining a resistance for each current path; and

if a difference in resistance between any two of the plurality of charging switch units is higher than a predetermined threshold value, controlling the contact force of a contactor in a charging switch unit in a current path having a deviating resistance to balance the resistances of the current paths.

12. The method according to claim 11 , wherein controlling the contact force of the contactor comprises controlling the current supplied to a coil of an electromagnetic relay.

13. The method according to claim 11 , wherein controlling the contact force of the contactor comprises controlling a position of a stepper motor in the contactor.

14. The method according to claim 11 , wherein the charging control unit is further configured control the contact force to reduce the current in any charging switch unit having a temperature above a predetermined threshold temperature.

15. The method according to claim 11 , further comprising:

determining a resistance for each current path through a charging switch unit; and

if a resistance in any one current path is deviating from resistances in other current paths by more than a predetermined threshold value, controlling the contact force for the contactor in the one or more current path with the deviating resistance to equalize the resistance for all current paths.